If President Donald Trump's threat to tariff Canadian imports by 25% goes forward, 200 years of peaceful and profitable Great Lakes maritime trade will be at risk.

In 2002, the Great Lakes basin had just 11.9% ice coverage, NOAA said. In 2012, Lake Superior had 8.5% coverage. In 2002, Lake Michigan had 12.4% coverage. In 2012, Lake Huron had 22.8% coverage.